In certain types of medical emergencies, Cardio-Pulmonary Resuscitation (“CPR”) needs to be delivered to a patient. CPR includes repeatedly compressing the chest of the patient, to cause their blood to circulate some. CPR also includes delivering rescue breaths to the patient. A number of people are trained in CPR, just in case, even though they are not trained in the medical professions.
The chest compressions are intended to prevent damage to organs like the brain. In some instances, the chest compressions merely maintain the patient, until a more definite therapy is made available, such as defibrillation. Defibrillation is an electrical shock deliberately delivered to a person, in the hope of correcting their heart rhythm.
A problem is that CPR is sometimes ineffective for preventing damage to the patient. That can happen whether or not the rescuer who performs the CPR is part of the medical profession. The most frequent example of such ineffectiveness is compressions that are not deep enough, or not frequent enough. Even the best trained rescuers can become fatigued after delivering CPR, with the compressions deteriorating in quality. And that is without even accounting for the emotions of the moment, which might impact a lay rescuer.
The risk of ineffective chest compressions has been addressed in part by defibrillator manufacturers. Some defibrillators nowadays issue verbal and visual prompts and other instructions as to how CPR is to be performed. These are often according to the guidelines of medical experts, such as the American Heart Association. These prompts and other instructions can help the rescuer focus better, even if the latter cannot remember their training.
The risk of ineffective chest compressions has been additionally addressed with CPR feedback devices. These devices actually detect the depth and frequency of compressions that the rescuer is performing, and give feedback that is specifically attuned to what the rescuer is doing. This feedback can be in accordance with the how well the rescuer is meeting the above mentioned guidelines, especially in achieving the indicated depth of compressions.
Reaching the appropriate depth is difficult. The recommended depth is a range. If the actual depth is less than the range, not enough blood is moved within the patient. If the depth exceeds the range, the patient's ribs may break. And, even for experienced rescuers, it is sometimes hard to discern the appropriate depth. Reaching the appropriate depth is even more difficult if the patient is on a flexible mattress that partly recedes, as the rescuer is pushing from the top. And CPR compressions are even more challenging, if the rescuer has to deliver them in a moving ambulance.
The risk of ineffective chest compressions has been moreover addressed with CPR chest compression machines. Such machines have been known by a number of names, such as mechanical CPR devices, cardiac compressors, external chest compression machines, and so on.
CPR chest compression machines repeatedly compress and release the chest of the patient. Such machines can be programmed so that they will compress and release at the recommended rate, and always reach a specific depth within the recommended range.
Although CPR chest compression machines can be used in conjunction with external defibrillators, not all ailments for which a CPR chest compression machine is used require defibrillation. Hence, many treatment protocols instruct the use of CPR without the need to electrically shock the patient's heart.
Although it is generally good to perform CPR chest compressions, it is sometimes difficult to know when to stop compressions. A CPR machine, or even a rescuer may not notice that a patient has regained spontaneous circulation and compressions may continue to be given even though the patient's heart is beating. Occasionally the patient may regain consciousness during compressions. This may cause the patient pain and discomfort, as well as potentially scaring them and causing additional emotional or physical trauma.
Even when the CPR chest compression machine helps the patient return to spontaneous circulation while they are still comatose, it is still desirable to stop the CPR chest compression machine promptly because 1) its compressions can interfere with the normal filling of heart chambers between spontaneous heart contractions, thus decreasing the cardiac output caused by those spontaneous heart contractions, and 2) its compressions can, under certain circumstances, increase the probability that the heart will return to ventricular fibrillation.